After the Earth-shaking announcement last week that they'd discovered an arsenic-based life form, NASA researchers are under attack from many in the scientific community. Experts are calling the research shoddy, and wondering if NASA is just desperate for publicity.

Last week, NASA held a press conference to announce the new organism, which they teased with a fairly misleading media release that suggested they'd discovered life on another world: They promised to announce "an astrobiology finding that will impact the search for evidence of extraterrestrial life." The media release had the intended effect: News organizations were in a tizzy. But when reporters (including io9's Alasdair Wilkins) got to the press conference, they discovered that NASA wasn't talking about astrobiology at all, but instead an Earth-based microbe that resembled what scientists speculate life on other planets might be like. (Read io9's report on the press conference here.)

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The new microbe was exciting in itself, though. NASA scientists had discovered its DNA was held together with arsenic rather than the phosphates that underpin the DNA of all other known organisms on Earth. Truly, it was a form of life we'd never seen before, and proved that the building blocks of life didn't have to rely on the same chemicals most of us on Earth do.

But now a huge number of scientists have stepped forward to question the methods of the NASA team. Writing on their blogs and in other media outlets, they're saying that the NASA scientists made basic errors in the way they handled the DNA samples. Over at Slate, Carl Zimmer reports on the results of his interviews with a dozen experts in the field of exotic microbes:

None of the scientists I spoke to ruled out the possibility that such weird bacteria might exist. Indeed, some of them were co-authors of a 2007 report for the National Academies of Sciences on alien life that called for research into, among other things, arsenic-based biology. But almost to a person, they felt that the NASA team had failed to take some basic precautions to avoid misleading results.

When the NASA scientists took the DNA out of the bacteria, for example, they ought to have taken extra steps to wash away any other kinds of molecules. Without these precautions, arsenic could have simply glommed to the DNA, like gum on a shoe. "It is pretty trivial to do a much better job," said Rohwer.

In fact, says Harvard microbiologist Alex Bradley, the NASA scientists unknowingly demonstrated the flaws in their own experiment. They immersed the DNA in water as they analyzed it, he points out. Arsenic compounds fall apart quickly in water, so if it really was in the microbe's genes, it should have broken into fragments, Bradley wrote Sunday in a guest post on the blog We, Beasties. But the DNA remained in large chunks-presumably because it was made of durable phosphate. Bradley got his Ph.D. under MIT professor Roger Summons, a professor at MIT who co-authored the 2007 weird-life report. Summons backs his former student's critique.

The NASA research team has refused to comment on these criticisms, saying that the proper place for such debates is in scientific journals and the lab, where they hope other scientists will examine the microbes for themselves before drawing any further conclusions. Fair enough, but as Zimmer's sources point out, it's not as if these same scientists weren't courting media attention with their misleading press release. Not only that, but they announced their findings at a press conference to coincide with the publication of their paper in Science. It's fairly unusual for scientists to hold press conferences about their work, so this about-face on the part of the NASA researchers seems a little hypocritical.

Some scientists are left wondering why NASA made such a big deal over a paper with so many flaws. "I suspect that NASA may be so desperate for a positive story that they didn't look for any serious advice from DNA or even microbiology people," says John Roth of UC-Davis. The experience reminded some of another press conference NASA held in 1996. Scientists unveiled a meteorite from Mars in which they said there were microscopic fossils. A number of critics condemned the report (also published in Science) for making claims it couldn't back up. And today many scientists think that all of the alleged signs of life in the rocks could have just as easily been made on a lifeless planet.

At this point, the next step is for other scientists to test these new microbes in the lab for themselves, and publish their own findings. Let's hope these criticisms are unfounded - for the sake of NASA's reputation during a difficult time for the agency, and for the sake of our hopes that the future of life lies beyond what we know already.